Immobilized Metal Affinity Chromatography of Phosphorylated Proteins Using High Performance Sorbents

The interactions of two model phosphoproteins (porcine pepsin and ovalbumin) with two different immobilized metal affinity chromatography (IMAC) sorbents containing immobilized Fe³⁺, Ga³⁺, and UO₂ ²⁺ ions have been investigated under various conditions. Both proteins were adsorbed on immobilized uranyl ions under acidic conditions similar to those on immobilized Fe³⁺ and Ga³⁺ ions. The retained proteins could be released either by the presence of phosphate ions in the elution buffer (immobilized Ga³⁺ and Fe³⁺ ions) or by an increased pH (all tested immobilized ions). The IMAC sorbents employed could be used under the conditions of high-performance chromatography and are suitable for the separation and analysis of intact phosphoproteins.     

Application of thermal analysis in the selection of polymer components used as a binder for metal injection moulding of Co–Cr–Mo alloy powder

Studies on the separation of calcium and neodymium ions by using ethylenediaminetetraacetic acid (H₄EDTA) as a complexing agent were performed. This research was undertaken due to the possibility of H₄EDTA applying to isolate rare earth elements from the solution after acidic leaching of phosphogypsum, and because of the similarity of coordination properties of calcium and lanthanides ions. The experiment was carried out in model systems containing Ca²⁺ and Nd³⁺ ions in hydrochloric or sulphuric acid. The content of calcium and neodymium metals, phase composition and thermal behaviour of the obtained products were determined by ICP-OES, FTIR, XRD and TG/DTA techniques. During the separation process, the precipitates of a light pink colour were obtained. The obtained results show that the neodymium ethylenediaminetetraacetate has been successfully formed and that the isolation of neodymium ions was more efficient in chloride medium. The precipitate included 72.2 and 3.9% of the starting amount of neodymium and calcium used in the experiment, respectively. However, in sulphates medium, these amounts were equal to 73.8 and 53.5%, respectively. Moreover, the obtained powder was polluted with sulphates. The addition of the EDTA in an excess (15%) contributed only to an increase in calcium content in the complex.

     

Response characteristics of a potentiometric detector with a copper metal electrode for flow-injection and chromatographic determinations of metal ions

The potentiometric response characteristics of a copper metal indicator electrode are reported in a flow-injection system when metal ions are injected into ligands of differing complexing strengths in buffered carrier streams. Theoretical Nernstian derivation of equations relating peak heights to both the injected metal ion concentration and the ligand concentration are shown to give good agreement with experimental peak height measurements for Ca²⁺, Al³⁺, Pb²⁺, Cd²⁺, Co²⁺, Cu²⁺, Ni²⁺, Mn²⁺, Zn²⁺ and UO²⁺₂. A study of injections into buffered ligand streams containing EDTA, ethylenediamine, triethylenetetramine, iminodiacetate, citrate, or glutamate shows advantages for the use of the more weakly complexing ligands in the carrier stream. Linear response are obtained at low (10^?3–10^?4 M) metal ion concentrations over narrow ranges. Some chromatographic applications are outlined.     

Spectrophotometric studies on the uranyl-ascorbate complex

A systematic spectrophotometric study on the complexation of uranyl ions with ascorbic acid (vitamin C) is carried out. Factors influencing the sensitivity or selectivity of uranyl ascorbate are studied, and adequate elimination or control of the procedure is suggested. Results of the absorbance of uranyl ascorbate developed in HNO₃, HCl, and H₂SO₄ acid media within the concentration range (1.0–8.0) × 10⁻N show a marked dependence on the nature and concentration of the acid used. The observed decrease in color intensity at higher acidities is explained on the basis of the decomposing effect of hydrogen ions on uranyl ascorbate and the complexing effect on uranyl ions. Study of the stoichiometry of uranium:ascorbic acid complex in acid medium by continuous variation and molar ratio methods indicated the formation of 1:1 and 1:2 complexes. The formation constant of the 1:1 complex as calculated by these two methods was found to be 4.8 × 10⁴ and 5.0 × 10⁴, respectively. Best suitable conditions for stabilizing and increasing the color intensity of uranyl ascorbate, dependent on the nature of the medium and pH of the solution, are suggested for the determination of ascorbic acid in pharmaceutical preparations using this method.     

Metal Analyses in Environmental and Pharmaceutical Samples by Capillary Electrophoresis with Methyl 3‐Amino‐3‐(pyridin‐3‐yl)propanoate Dihydrochloride as a New Ion‐Pairing Reagent

Separation and determination of some common metal ions was achieved with methyl 3‐amino‐3‐(pyridin‐3‐yl)propanoate dihydrochloride (MAPP) as an ion‐pairing reagent and pyridine as a detectable counter‐ion for indirect UV detection at 254 nm. The effects of the complexing reagent and chromophore concentrations, applied voltage, and organic solvent content on the separation were investigated. The optimized separation was carried out in a running electrolyte containing 16 mM MAPP and 20 mM pyridine at pH 4.0 and was successfully applied to the qualitative and quantitative analysis of Li⁺, Na⁺, Mg²⁺, Ca²⁺, Ba²⁺, Ni²⁺, and Zn²⁺ in pharmaceutical vitamin preparations and various water samples.     

Complexation of poly(acrylic acid)s with uranyl ion

The complexation of uranyl ion (UO₂²⁺) in aqueous solution with polymers containing carboxylic acid groups was studied potentiometrically. Overall formation constants of the uranyl complexes with poly(methacrylic acid) and crosslinked poly(acrylic acid) were much larger than those with the corresponding low molecular carboxylic acids. Decrease in the viscosity of the polymer solution on adding uranyl ion indicated that poly(acrylic acid) forms intra-polymer chelates with uranyl ion. The crosslinked poly(acrylic acid) adsorbed uranyl ions at higher efficiency than transition metal ions.     

Reduction–Oxidation of Chromium Ions in Aqueous Solution by Treatment with Atmospheric-Pressure Direct-Current Discharge in Argon

Kinetic features of the oxidation–reduction processes of chromium ions in a potassium dichromate aqueous solution subjected to treatment in argon atmospheric-pressure dc discharge have been investigated in the discharge current range of 20–80 mA and the dichromate concentration range of 0.1–0.5 mmol/L. The solution served as the discharge cathode. It has been revealed that the discharge treatment stimulates the reduction reactions of Cr⁶⁺ to Cr³⁺ ions and the reverse reactions of oxidation of Cr³⁺ to Cr⁶⁺ ions; i.e., the oxidation–reduction reactions are reversible. The limiting degree of reduction of Cr⁶⁺ ions has been found to depend on the discharge current and the initial concentration of the solution. The apparent rate constants of oxidation and reduction have been determined, and the energy efficiency of the process has been evaluated. The data are compared with the results obtained earlier for a discharge in air.     

Combining electrolysis and dialysis for regeneration of chromic acid etching solution

The technique of integrating Donnan dialysis with electrolysis was evaluated for regenerating a chromic acid solution contaminated with copper. Electrolysis converts the reduced chromium (Cr³⁺) to the active form (Cr⁶⁺, as dichromate), but cannot remove copper efficiently. A dialyzer in series greatly increases the copper removal efficiency by providing a facile route for copper ions to reach the catholyte where they are electrodeposited.     

Metal-Carboxyl Helical Chain Secondary Units Supported Ion-Exchangeable Anionic Uranyl–Organic Framework

As a less explored avenue, actinide-based metal-organic frameworks (MOFs) are worth studying for the particularity of actinide nodes in coordination behaviour and assembly modes. In this work, an azobenzenetetracarboxylate-based anionic MOF supported by uranyl–carboxyl helical chain units was synthesized, incorporating linear uranyl as the metal centre. This kind of helical chain-type building unit is reported for the first time in uranyl-based MOFs. Structural analysis reveals that the formation of helical chain secondary units can be attributed to restricted equatorial coordination of rigid flat azobenzene ligand to uranyl centres. Meanwhile, this newly-synthesized anionic material has been used to remove Eu³⁺ ions, as a non-radioactive surrogate of Am³⁺ ion, through an ion-exchange process with [(CH₃)₂NH₂]⁺ ions in its open channels, as evidenced by a combination of ¹H NMR spectroscopy, EDS and PXRD.     

Complexometric and spectrophotometric determination of thorium(IV), cerium(III), and uranium(VI), using quinizarin sulphonic acid after separation with ion-exchange resins

A method is described for the complexometric EDTA-titration and spectrophotometric determination of Th⁴⁺ Ce³⁺, and UO₂²⁺ in binary or ternary mixtures after primary separation with ion-exchange resin. As indicator or coloring agent, quinizarin sulphonic acid is used. The EDTA titration gives accurate results with Th⁴⁺ and Ce³⁺ only, but the spectrophotometric method proved to be suitable for determination of small quantities of the metal ions.     

Separation and concentration of cobalt from ammoniacal solutions containing cobalt and nickel by emulsion liquid membranes using 5,7-dibromo-8-hydroxyquinoline (DBHQ)

The separation and concentration of cobalt from ammoniacal solutions containing nickel and cobalt by an emulsion liquid membranes (ELMs) using 5,7-dibromo-8-hydroxyquinoline as extractant has been presented. Membrane solution consists of a diluent (kerosene), a surfactant (Span 80), a modifier (tributylphosphate), and an extractant (DBHQ). Very dilute sulphuric solution containing EDTA as complexing agent, buffered at pH 5.0, has been used as a stripping solution. pH of ammoniacal feed solution containing cobalt and nickel was adjusted to 9.0 with hydrochloric acid. The important variables governing the permeation of cobalt have been studied. These variables are membrane composition, pH of the feed solution, cobalt and nickel concentrations of the feed solution, mixing speed, surfactant concentration, extractant concentration, EDTA concentration and pH of the stripping solution, and phase ratio. After the optimum conditions had been determined, it was possible to selectively extract 99.0% of cobalt from ammoniacal feed solution containing Co²⁺ and Ni²⁺ ions. The separation factors of cobalt with respect to nickel, based on initial feed concentration, have experimentally found to be of as high as 247.5 for about equimolar Co–Ni feed solutions.     

Polymeric Membrane Lanthanum(III)‐Selective Electrode Based on N,N′‐Adipylbis(5‐phenylazo salicylaldehyde hydrazone)

A recently synthesized azao‐containing Schiff's base N,N′‐adipylbis(5‐phenylazo salicylaldehyde hydrazone) was used as a suitable neutral ion carrier in construction of a highly selective La³⁺‐PVC membrane electrode. The electrode exhibits a Nernstian response with a slope of 19.4 mV decade^?1 over a wide concentration range (1.0×10^?6–1.0×10^?2 M) and a limit of detection of 4.0×10^?7 M (0.05 ppm). The electrode possesses a fast response time of ca. 10 s and can be used for at least 3 months without observing any deviation. The proposed electrode revealed excellent selectivity for La³⁺ over a wide variety of alkali, alkaline earth, transition and heavy metal ions and could be used in a pH range of 4.0–8.0. The practical utility of the electrode has been demonstrated by its use as an indicator electrode in the potentiometric titration of La³⁺ ions with EDTA and in determination of F^? ion in some pharmaceutical preparations.     

Utilisation de matériaux à base d’argiles modifiées dans la conversion du toluène

Clay materials, montmorillonite from Maghniya deposits (Algeria), were used as an acidic catalyst in toluene conversion. Toluene disproportionation reaction in gaseous phase was used. These clays were modified by ion exchange with uranyl ions UO₂²⁺. The surface acidity of catalysts was determined by the stepwise desorption technique (STD) of probe molecules using butylamine and ammonia. Thus, total acidity and distribution of the acidity strength were determined. The results show that materials presented an appreciable total acidity and catalytic activity in studied reaction. The acidity strength of catalysts due to UO₂²⁺ ions was kept at a temperature of 550 °C. A relationship was found between the catalytic activity and acidity strength generated by the introduction of uranyl ions in the clay structure.     

Separation and direct UV detection of complexed lanthanides,thorium and uranyl ions with 2-thenoyltrifluoroacetone by using capillary zone electrophoresis

Separation and detection of lanthanides, thorium and uranyl ions by capillary zone electrophoresis in the presence of 2-thenoyltrifluoroacetone (HTTA) as UV-absorbing complexing agent were investigated. The separation of positively charged complexes is partially improved by using a competing ligand in buffer with HTTA for metal ions. When 2-hydroxyisobutyric acid (HIBA) is used as competing ligand, complete separation of thorium, uranyl and lanthanides ions were observed. Some separation parameters such as pH value, the concentration of carrier electrolyte, applied voltage, the concentration of ligand in buffer and the temperature were also optimized. Under the selected conditions, the complete separation of thorium and uranyl from each other and from lanthanides was accomplished in only 12 min using 1 mmol/L HTTA, 50 mmol/L HIBA, 5 mmol/L NaNO₃, 5 % methanol with a pH 5.2 at a capillary temperature of 25 °C. Direct photometric detection at 210 nm using a voltage of 25 kV and an electrokinetic injection (100 mm for 6 s) were used.     

A fast and simple method for the estimation of natural uranium in urine

Natural uranium (U) in urine was co-precipitated with Ca₃(PO₄)₂ and then with BiPO₄ after reducing uranyl ions from +6 to +4 state. U separated from BiPO₄ was then quantified by measuring its absorbance after complexing it with Arsenazo-III. The interference caused by ions such as Fe³⁺, Bi³⁺, Zn²⁺ and PO₄ ³⁻ was studied during the measurement of U absorbance. The percent recovery of U was 81.4±2.6 for 5 to 30 μg U present in 500 ml urine. The minimum detectable concentration of U was 2 μg/l and the time required to complete the analysis was 2 days.     

Ethylenediaminetetraacetic Acid Functionalized Gold Nanoparticles for Sensitive Colorimetric Detection of Chromium(III)

A cost‐effective and sensitive colorimetric method was described for the determination of chromium(III) ion (Cr³⁺) by using ethylenediaminetetraacetic acid functionalized gold nanoparticles (EDTA‐AuNPs) as a probe. The stable and dispersed EDTA‐AuNPs were prepared by reducing HAuCl4 with sodium borohydride in presence of EDTA as a capping agent. Upon the addition of Cr³⁺, the colour of EDTA‐AuNPs solution changed from red to violet, which was in response to the surface plasmon absorption of dispersed and aggregated EDTA‐AuNPs. The procedure allowed the determination of Cr³⁺ in the range of 0.1–1.0 mol/L. The limit of detection for Cr³⁺ was 0.08 mol/L. The relative standard deviation was 2.5 % for eight repeated measurements of 0.6 mol/L Cr³⁺ solution. The method was applied to the determination of Cr³⁺ in water samples.     

Coupling of an electrodialyzer with inductively coupled plasma mass spectrometry for the on-line determination of trace impurities in silicon wafers after surface metal extraction

Understanding the properties that determine the distribution and behavior of trace impurities in Si wafers is critical to defining and controlling the performance, reliability, and yields of integrated microelectronic devices. It remains, however, an intrinsically difficult task to determine trace impurities in Si because of the minute concentrations and extremely high levels of matrix involved. In this study, we used an electrodialyzer for the simultaneous on-line removal of the silicate and acid matrices through the neutralization of the excessive hydrogen ion and selectively separation of acid and silicate ions by the combination of electrode reaction as a source of hydroxide ions with the anion exchange membrane separation. To retain the analyte ions in the sample stream, we found that the presence of moderate amounts of nitric acid and hydrazine were necessary to improve the retention efficiency, not only for Zn²⁺, Ni²⁺, Cu²⁺, and Co²⁺ ions but also for CrO₄²⁻ ion. Under the optimized conditions, the interference that resulted from the sample matrix was suppressed significantly to provide satisfactory analytical signals. The precision of this method was ca. 5% when we used an electrodialyzer equipped with an anion exchange membrane to remove the sample matrix prior to performing inductively coupled plasma mass spectrometry (ICP-MS); the good agreement between the data obtained using our proposed method and those obtained using a batchwise wet chemical technique confirmed its accuracy. Our method permits the determination of Zn, Ni, Cu, Co, and Cr in Si wafers at detection limits within the range from 2.2 × 10¹⁵ to 9.0 × 10¹⁵ atoms cm⁻³.     

Synergistic coupled transport of uranyl ion across bulk liquid membrane mediated by dioxa-diazamacrocycle and oleic acid

Synergistic coupled transport of uranyl ion across a bulk liquid membrane of chloroform has been investigated using a dioxa-diazamacrocycle and oleic acid as carrier and synergistic agents, respectively. Quantitative transport of uranyl ion was achieved within 4 h when the pH of source solution was kept at 5.0–6.0 and mole ratio of carrier to synergistic agent was 1/15. It was found that overall rate and selectivity of the transport is governed by the stripping step. Finally, the influence of some foreign competitor ions including Al³⁺, Ca²⁺, CO₃^2?, Cu²⁺, Mg²⁺, Pb²⁺, Zn²⁺ and Th⁴⁺ and also the ionic strength on the transport efficiency has been evaluated.     

Effect of Complexation on Photocatalytic Degradation of Dissolved Organic Nitrogen Compounds

Abstract

The effect of metal ions on TiO₂ mediated photocatalytic oxidation for the determination of dissolved organic nitrogen compounds is investigated. Ethylenediaminetetraaceticacid was chosen as a model molecule for DON compounds. At pH 2, 5, 7, and 10 aqueous EDTA solutions were irradiated at 254 nm in the presence of Fe²⁺, Cu²⁺, Zn²⁺, Ni²⁺ or Co²⁺ ions. The sum of produced nitrate, nitrite, and ammonium ion concentrations gave the total oxidation recovery. At low pH, the photocatalytic oxidation recoveries of Fe‐EDTA, Ni‐EDTA, and Co‐EDTA were significantly lower than the photocatalytic degradation of EDTA. The presence of free Fe²⁺, Ni²⁺, and Co²⁺ ions decreased the photocatalytic oxidation recovery. The [NH₄ ⁺]/[NO₃ ^?] ratio was higher for Cu‐EDTA.     

Adsorption of Uranyl Ions into Poly(Acrylamide‐co‐Acrylic Acid) Hydrogels Prepared by Gamma Irradiation

Acrylamide (AAm)/Acrylic Acid (AAc) copolymers have been prepared by gamma irradiation of binary mixtures at three different compositions where the acrylamide/acrylic acid mole ratios varied around 15, 20, and 30%. Threshold dose for 100% conversion of monomers into hydrogels was found to be 8.0 kGy. Poly(Acrylamide‐co‐Acrylic Acid) (poly(AAm‐co‐AAc)) hydrogels have been considered for the removal of uranyl ions from aqueous solutions. Swelling behavior of these hydrogels was determined in distilled water at different pH values and in aqueous solutions of uranyl ions. The results of swelling tests at pH 8.0 indicated that poly(AAm‐co‐AAc) hydrogel, containing 15% acrylamide showed maximum % swelling. Diffusion of water and aqueous solutions of uranyl ion into hydrogels was found to be non‐Fickian in character and their diffusion coefficients were calculated. The effect of pH, composition of hydrogel, and concentration of uranyl ions on the adsorption process were studied at room temperature. It was found that one gram of dry poly(AAm‐co‐AAc) hydrogel adsorbed 70–320 mg and 70–400 mg uranyl ions from aqueous solutions of uranyl nitrate and uranyl acetate in the initial concentration range of 50–1500 mg UO₂ ²⁺L^?, depending on the amount of AAc in the hydrogels, respectively. Adsorption isotherms were constructed for poly(AAm‐co‐AAc)–uranyl ion system indicating an S type of adsorption in the Giles classification system. It is concluded that crosslinked poly(AAm‐co‐AAc) hydrogels can be successfully used for the removal of uranyl ions from their aqueous solutions.